J. Nannoplankton Res. 29 (2), 2007, pp.78-87 © 2007 International Nannoplankton Association
ISSN 1210-8049 Printed by Cambridge University Press, UK

78

Living Braarudosphaera bigelowii (Gran & Braarud)
Deflandre in the Bering Sea
Susumu Konno
Division of Interactive Symbiosphere Sciences, Graduate School of Science & Engineering, Yamagata University, 1-4-12 Kojirakawa-machi,
Yamagata 990-8560, Japan

Naomi Harada
Institute of Observational Research for Global Change, Japan Agency for Marine-Earth Science & Technology, 2-15 Natsushima-cho, Yokosuka
237-0061, Japan

Hisashi Narita
Department of Marine Science, School of Marine Science & Technology, Tokai University, 3-20-1 Orido, Shimizu-ku, Shizuoka 424-8610, Japan

Richard W. Jordan*
Department of Earth & Environmental Sciences, Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata 990-8560, Japan;*sh081@kdw.kj.yamagata-u.ac.jp
Manuscript received 2nd May, 2007; revised manuscript accepted 15th September, 2007

Abstract During the MR06-04 cruise of the R/V Mirai in summer, 2006, surface and subsurface water-samples
were extensively collected from the eastern Bering Sea. In a small number of these samples, Braarudosphaera
bigelowii was detected in relatively low absolute abundances. Their presence in the Bering Sea may represent thehighest boreal-latitude occurrence reported so far. Scanning electron microscope observations have revealed thepresence of two types of coccosphere, one with flattened faces, and one with somewhat concave faces. Regardlessof this coccosphere morphology, most of the pentalith dimensions correspond to the so-called ‘intermediate B’ form.
The coccospheres of B. bigelowii were mostly found in an area associated with a mesoscale bloom of Emiliania huxleyi. The hydrographic conditions of this bloom water generally support the hypothesis that B. bigelowii prefers lowsalinity, nutrient-rich coastal waters. Here, we report on the ecology and distribution of B. bigelowii, as well as themorphology of the two coccosphere types and their taxonomic significance.
Keywords Bering Sea, Braarudosphaera bigelowii, living nannoplankton assemblages, morphology
1. Introduction
Although there are numerous and well documented
reports of coccolithophorids from the North Pacific (e.g.
Okada & Honjo, 1973; Nishida, 1979; Reid, 1980;
Hagino, 1997; Hagino et al., 2000), few studies have dealt
with their presence in the Bering Sea. In fact, most of theBering Sea papers relate to the recent occurrence ofEmiliania huxleyi blooms on the eastern continental shelf(Sukhanova & Flint, 1998; Vance et al., 1998; Stockwell
et al., 2001; Olson & Strom, 2002; Shin et al., 2002;
Merico et al., 2004; Nishitani & Zhang, 2005). Of thosethat have recorded the coccolithophorid assemblages inother parts of the Bering Sea, the general picture seems to
be one of low diversity and low abundance, with E. huxleyi and Coccolithus pelagicus being the main two components (Takahashi et al., 2002; Tanimoto et al., 2003;
Hattori et al., 2004).
Micranthrolithus was the most abundant braarudospherid throughout much of the Early Cretaceous, before
Braarudosphaera replaced it in the mid-Cretaceous, with
Braarudosphaera-rich sediments being laid down during
the Turonian in various locations around the world(Cunha & Shimabukuro, 1997; Burnett et al., 1998;
Svábenická, 1999). Braarudosphaera became less abundant during the Late Cretaceous and Paleocene, but there
were consistent occurrences in the Eocene, as well as
exceptional intervals like the Cretaceous/Tertiary bound-ary (Bown, 2005). Braarudosphaera declined again after
the Eocene, and this general trend continued throughout
the Late Cenozoic, apart from sporadic occurrences ofBraarudosphaera-rich sediments during the Oligocene(Parker et al., 1985; Siesser et al., 1992; Peleo-Alampay
et al., 1999; Kelly et al., 2003).
In the last 50 years, many coccolith workers havereported the presence of Braarudosphaera in the surfacesediments of nearshore environments, especially around
Japan (Takayama, 1972; Nishida & Konda, 1974;
Nishida, 1981; Tanaka, 1991), but also in other parts of
the world (Martini, 1967; Scholle & Kling, 1972; Bukry,
1974; Zhang & Siesser, 1986; Ferreira & Cachão, 2005;
Giunta et al., 2007). Today, Braarudosphaera can befound in the Norwegian Sea (Heimdal, 1993), in coastal
waters off Portugal (Duarte-Silva et al., 2004), off western North Africa (Lecal-Schlauder, 1950, as ‘B.
Deflandrei’; Heimdal & Gaarder, 1981), in the
Mediterranean Sea (Borsetti & Cati, 1972;
Knappertsbusch, 1993), off eastern North America (Gran& Braarud, 1935; Bérard-Therriault et al., 1999), in the
Sargasso Sea (Gaarder, 1954; Hulburt, 1962; Hulburt &Rodman, 1963), in the Gulf of Panama (Smayda, 1966),
off Australia (Hiramatsu & De Deckker, 1996; Takahashi& Okada, 2000), off Japan (Hagino, 1997; Takano et al.,2006), and in the North Pacific (Nishida, 1979). It should
be noted that Braarudosphaera bigelowii has also been

79

Konno, Harada, Narita, Jordan

concentrations of up to 110 x 103 cells/litre.
Here, we report the finding of Braarudosphaera coccospheres in Bering Sea surface-waters, possibly for the
first time, and perhaps from the highest latitude.

Figure 1: General location of the study area (inset) and location of thesamples containing B. bigelowii. Black circles indicate CTD stations,open circles indicate underway sites. Maps created using Martin
Weinelt’s ‘Online Map Creation’ site at www.aquarius.ifm-geomar.de

recorded in sediment trap studies from the Bay of Biscay(Beaufort & Heussner, 2001) and the Sea of Okhotsk(Broerse et al., 2000), although living populations havenot been reported from either of these two locations. In
general, the absolute abundance of B. bigelowii is low and
it is usually a rare component in nannoplankton assemblages, however, Duarte-Silva et al. (2004) reported cell

2. Material and methods
During Leg 2 of the MR06-04 cruise of the R/V Mirai (aresearch ship belonging to the Japan Agency for MarineEarth Science & Technology - JAMSTEC), in the summerof 2006, surface and subsurface water-samples were collected at various stations in the Bering Sea. Most surfacewater samples were acquired while the ship was underway, using the shipboard sea-water supply (for researchuse), which is obtained via an intake pipe located 4m
below the ship. In the case of these underway samples, 14l of sea-water were collected in plastic bottles with thefollowing information recorded at the time of sampling:
the date and (Greenwich Mean) time, geographic coordinates, and those parameters (such as temperature, salinity,
fluorescence and dissolved oxygen) being continuously
recorded by instruments connected to the sea-water supply. Of the 165 samples collected using this method during Leg 2 of MR06-04, only eight are presently known tocontain Braarudosphaera coccospheres (see Figure 1,
Table 1). These samples were given a ‘KS’ notation (theinitials of the sample collector, Konno Susumu) to distinguish them from Conductivity Temperature Depth (CTD)
sites (labeled ‘St.’). An additional underway sample,
labeled ‘Cocco’, was obtained by Hisashi Narita.
Subsurface samples were obtained using a rosette ofwater-bottles attached to a CTD rig, with about three toeight depths selected from each of the 15 shallow anddeep hydrocasts conducted in the Bering Sea. During
shallow hydrocasts, measurements and samples are usually taken in the top 200-300m (i.e. in the photic layer),while for deep hydrocasts, the entire water-column (e.g.

Site/Station number Latitude (˚N) Longitude (˚W) Sample depth (m) Temperature (˚C)
KS-05656.64
167.09surface
10.49
KS-05757.52
167.32surface
10.08

Salinity
31.82
31.27

Depth to sea-bed (m)ca .70ca .70KS-111
KS-119KS-120

58.4
58.04
57.43

169.96169.38168.23surfacesurfacesurface

7.54
7.25
7.07

31.23
31.33
31.7

ca .70ca .70ca .70KS-127
KS-128

57.42
57.38

167.34167.32surfacesurface

7.34
7.32

31.47
31.48

ca .70ca .70KS-129
Cocco

57.17
57

167.24167.32surfacesurface

7.63
10.38

31.63
31.45

ca .70ca .70

St.19

63

167.5

58.38

170

7.33 (taken at 1m)
7.26
6.89
7.28

31.39 (taken at 1m)
31.39
31.45
31.24

34

St.31

0
10
24
10

St.32

57

167.5

0
10
20
30

7.58 (taken at 1m)
7.58
7.58
7.08

31.71 (taken at 1m)
31.71
31.71
31.76

65

3.35

32.27

Table 1: General information on the underway sites and CTD stations

70
74

Living Braarudosphaera bigelowii...Bering Sea

Chlorophyll a (µ g / l )Station number Sample depth (m) Total < 2 µ m
St.19
0
0.56
0.48
10
0.49
0.40
24
2.80
0.45
St.31
10
3.15
0.97
St.32
0
7.13
0.66
10
7.43
1.12
20
7.44
1.16

2-5µ m
0.03
0.05
0.53
0.73
0.67
0.56
0.54

5-10µ m > 1 0 µ m
0.02
0.03
0.02
0.02
0.29
1.53
1.15
0.3
0.74
5.06
0.9
4.85
1.07
4.67

80

curated in the Department of Earth & Environmental
Sciences, Faculty of Science, Yamagata University.

3. Observations
Braarudosphaera bigelowii coccospheres were encountered at three CTD stations and nine underway samplingsites in the shallow waters over the eastern Bering Sea
continental shelf. At most of these stations and sites, the
30
8.44
0.72
0.72
0.56
6.44
surface and subsurface waters were characterised by an
65
0.56
0.05
0.08
0.15
0.28
Emiliania huxleyi bloom (Konno et al., in prep.). Thesewaters were relatively cool (7-10˚C) and with a low salinTable 2: Chlorophyll a at the three CTD stations
ity (31-32 PSU), while the environmental dataset from the
0-5000m) may be investigated. At each station, a bucket three CTD stations shows that the B. bigelowii coccoswas used to take a surface-water sample. About 2l sam- pheres were present in relatively high-chlorophyll, lowples of sea-water were collected in plastic bottles from nutrient waters (Tables 1-3). The highest absolute abunselected rosette bottles after the CTD rig had returned to dances were recorded in the surface-waters at underway
the ship. Unlike the underway samples, a more extensive sampling sites ‘Cocco’ (2749 cells/litre) and KS-057
suite of physico-chemical data is available for each CTD (1394 cells/litre), but significant numbers were also foundstation. Of the 76 samples collected in the Bering Sea at KS-056, KS-128 and at 24m and 20m water-depths atusing this method during this cruise, nine are presently CTD Stations 19 and 32, respectively (Table 4).
Two types of B. bigelowii coccosphere were recogknown to contain Braarudosphaera coccospheres. Thesenine samples, taken from various depths, were collected nised, one composed of liths with flat faces (Plate 1) andfrom three hydrocasts, Stations 19, 31 and 32 (see Figure the other composed of liths with concave faces (Plate 2).
Both types were present in relatively low absolute abun1, Table 1).
Chlorophyll a concentrations were measured, and dances in the Bering Sea (see Table 4), at either the same
sorted into four size-fractions: <2µm, 2-5µm, 5-10µm and sampling stations, or at stations in close proximity to each
>10µm (Table 2). Duplicate measurements of nutrient other. Other than the nature of the faces, the two types
concentrations were made, with values in Table 3 present- appear identical. The coccospheres, 13.5-15.3µm in diameter, are regular pentagonal dodecahedrons (i.e. with 12
ed as averages.
Water-samples were filtered through Millipore HA- faces) comprising 12 closely-fitting pentaliths (pentagotype polycarbonate filters or Advantec mixed cellulose nal coccoliths). Each pentalith, 8.0-9.0µm in length
ester filters (47mm diameter, 0.45µm porosity), using an (measured from peak to opposite margin) and with sides
Eyela Aspirator A-3S (Tokyo Rikakikai Co., Ltd.) filtra- 4.7-6.0µm long, is composed of five elements of equaltion apparatus, air dried and then stored in plastic petris- size (3.1-4.0µm in length; the distance between the twoparallel sides). The elements are isosceles trapezium inlides.
A 3 x 3mm portion of each filter was cut out and shape (NB in American English = isosceles trapezoid).
mounted onto an aluminium stub, coated with With respect to the shorter of the parallel sides, which isplatinum/palladium in an Eiko IB-3 ion sputter-coater and always located at the margin, adjacent elements are rotatexamined in a Hitachi S-2250N scanning electron micro- ed by a difference of 72˚ (as first noted by Deflandre,
scope. Photographs were taken with the camera attach- 1947). Since the corners of such a trapezium would touch
ment, using Fuji Neopan 120 SS black and white film. the circumference of a circle, the shape could also be
Absolute abundances were calculated using the same referred to as a cyclic quadrilateral. In some specimens,
the element-element boundaries within a single pentalith,
method as Jordan & Winter (2000).
All of the samples and negatives used in this study are and also of neighbouring pentaliths, are accentuated by a
low ridge (Pl.1, fig.2; Pl.2, fig.6).
Usually, there are no gaps between
the elements, but occasionally, in
Average nutrient concentration (µ m o l / l )concave forms, a star-shaped gap
Station number Sample depth (m)NitrateNitriteSilicate
Phosphate
can be seen at the centre of the penSt.19
0
0.28
0.08
5.54
0.67
10
0.26
0.07
5.39
0.67
talith (Pl.2, figs 7, 8). Although not
24
0.35
0.10
6.67
0.74
shown here, the pentaliths are thick,
St.31
10
1.404
0.035
3.293
0.522
laminated and distally flare (see
St.32
0
1.401
0.04
3.325
0.54
proximal views in Nishida &
10
1.404
0.035
3.293
0.522
20
1.392
0.04
3.284
0.525
Konda, 1974, pl.IX, fig.58; Tanaka,
30
10.7670.209
22.204
1.971
1991, pl.4, fig.9).
65
10.7540.23
22.268
1.976
In addition to the morphologicaldetails
given above, another feaTable 3: Macronutrient concentrations at the three CTD stations

81

Konno, Harada, Narita, Jordan

than 5.3µm (see Figure 2).
The finding of speciSite/Station number Sample depth (m) Volume filtered (l) Flat type Concave type Total (cells/l)mens with flat and concave
KS-056surface3
94518
faces is not novel, since
KS-057
surface326
91394
Young et al. (2003, p.80)
KS-111surface2
1
60
had already mentioned thisKS-119surface22
1
179
KS-120surface2
3
179
phenomenon. In their origiKS-127
surface2
3
179
nal description, Gran &KS-128surface1
4478
Braarud (1935, p.388)
KS-129surface2
1
60
noted that the coccoliths
Cocco
surface239
72749
were flat, however, their
St.19
0
1
2
239
fig.67 appears to represent a
10
1
3
359
coccosphere with concave
24
1
4
478
faces (compare Pl.2, fig.7
St.31
10
1
1
120
with Figure 3). If so, then
St.32
0
2
1
60
10
1
(1)
2(1)
239
the holotype of B. bigelowii
20
1
6
717
has concave faces and rep30
1
1120
resents intermediate form
65
2
3
179
B.
Should the two forms() signifies uncertainty of identification(with concave and flat
faces) turn out to be sepaTable 4: Raw data and absolute abundance of B. bigelowii coccospheres in the Bering Sea
rate entities in the future,
ture was commonly observed among both types of then the taxonomy of the B. bigelowii complex (most fosBraarudosphaera coccospheres. Many of the specimens sil pentaliths in Cenozoic sediments are currently
had particles attached to them, arranged along the margins assigned to the species) would also need to be reconsidof either the pentaliths or individual pentalith elements ered, since they all appear to bear flat faces. However, for(e.g. see Pl.1, figs 4, 6; Pl.2, figs 1, 2, 5). These could be the moment there is not enough evidence to determine
bacteria or, given their various shapes and sizes, particles whether or not this difference in the nature of the pentalthat had merely adhered to the coccoliths. Whatever they ith faces is taxonomically important. But this raises anothare, it is highly likely that their presence is related to er question. If the two types of face are produced by theorganic matter that has been secreted out of the same species (given their similar dimensions), what
Braarudosphaera cell, that is, through potential spaces caused the normally flat faces to become concave?
between abutting coccoliths and plate elements. Assuming of course that possession of flat faces is ‘norAlternatively, the particles on the coccolith surface could mal’, since, as mentioned above, most illustrated specibe blobs of organic matter that were forced out of the cell mens (both living and fossil) bear that type of face. If one
during filtration or desiccation of the filter onboard the considers the methodology used in this study, that is, filship.
tration and air-drying, then it is easy to imagine that, assome of the cells dried, the decreasing cell-volume pulled
4. Discussion
the pentalith elements inwards. However, why did it only
4.1 Morphological variation in modern
affect some of the coccospheres, as at many of our sites,
Braarudosphaera bigelowii
the nannoplankton assemblages contained both types (seeTakano et al. (2006) carried out morphometric studies on Table 2)? As mentioned above, Gran & Braarud (1935)
cultures of Braarudosphaera bigelowii isolated from the drew a specimen that had concave faces. This possibly
Tsugaru Strait, the seaway between the Japanese islands contradicts the desiccation theory, as their specimen wasof Hokkaido and Honshu, and showed that it has three almost certainly preserved and observed in liquid. Thus,size-classes, based on the side length of the pentalith: a the concave morphology may be a natural feature.
small form (<2.4µm), and two intermediate forms, A (4.0Although the presence of attached particles along the
5.3µm) and B (5.3-7.2µm). DNA variation between the lines of the element boundaries is described here for thelatter two forms suggested that they were distinct enough first time, other workers have shown specimens with theto be regarded as independent species. Gran & Braarud same feature (e.g. V. Pariente’s specimen at http://www(1935) stated that the coccosphere diameter of their new ocean.tamu.edu/Quarterdeck/QD5.2/b.bigelowi.html).
species, ‘Pontosphaera Bigelowi’, was 16µm. Using this Phytoplankton that leak cellular organic matter are often
measurement, Takano et al. (2006) calculated the pental- associated with symbionts or opportunistic organisms.
ith side length to be about 6µm (i.e. conforming to form Whilst no conclusive evidence exists for such a relationB). In general, our specimens also fit into this size-cate- ship in Braarudosphaera, it is known to grow in associagory, although some pentalith side lengths are smaller tion with Cyanophyceae under certain conditions, for
Coccospheres (raw data)Living Braarudosphaera bigelowii...Bering Sea

82

reported from ~70˚S (Cape Roberts Project, Ross Sea,
Antarctica: S.W. Wise, Jr., pers. comm. to RWJ, 2007).

Figure 2: Frequency distribution of pentalith side-lengths of B.
bigelowii specimens observed in this study (where n = 19; 10 with flat
faces, nine with concave faces). Measurements made on coccospheres
only. Size-categories taken from Takano et al. (2006)

example, in ‘l’eau de viviers’ (Chrétiennot-Dinet, 1990),
which could be translated as man-made ponds used forbreeding fish (i.e. fish farms).
4.2 Absolute abundances anddistribution of modern Braarudosphaera
bigelowii
In Figure 4, we have plotted all of those sites where living
Braarudosphaera bigelowii has been recorded. Given thelong stratigraphic range of this species ‘plexus’ in the fossil record (mid-Cretaceous to Present), and the difficulty
in separating out modern pentaliths from reworked pentaliths in surface sediments, we have resisted the desire toplot the locations of Recent fossil finds in Figure 4. In thisstudy, living populations of B. bigelowii were recorded forthe first time in the Bering Sea, albeit in low absoluteabundances (up to 103 cells/litre). However, these abundances are consistent with those found by most workers inother parts of the world (e.g. Smayda, 1966), except for
the high concentrations recorded by Duarte-Silva et al.
(2004). From Figure 4, it appears that our findings (i.e.
Station 19 in the Bering Sea) represent the highest latitude
that living Braarudosphaera has been found, althoughfossil pentaliths from the Lower Oligocene have been

Figure 3: Type illustration of ‘Pontosphaera Bigelowi’, reproduced
from Gran & Braarud (1935)

4.3 Ecology of Braarudosphaera
bigelowii
In the literature, Braarudosphaera bigelowii is often
described as a species living in low-salinity coastal
waters, since it is rarely recorded from the open ocean(e.g. Sargasso Sea: Gaarder, 1954; Hulburt, 1962). The
oceanographic conditions encountered in 2006 suggestthat B. bigelowii was growing (or entrained) in shallow
shelf waters that were relatively cool, with low salinity,and low concentrations of nutrients. Most of the
Braarudosphaera coccospheres were found in the area
affected by an Emiliania huxleyi bloom, hence the highconcentrations of chlorophyll a (although, oddly, the 25µm fraction was the lowest of the four categories).
Although it may be premature to directly associate B.
bigelowii with E. huxleyi blooms, the situation in 2006 isinteresting in many ways. Firstly, the distribution of B.
bigelowii shown in Figure 4 reveals that many of theselocations are also areas where E. huxleyi blooms havebeen reported from. Secondly, the conditions related tothese blooms are now widely available in the literature,and so some parallels can be drawn, assuming that thetiming of the blooms and the presence of B. bigelowii arecontemporaneous.
Merico et al. (2004) and Lessard et al. (2005) reported that E. huxleyi can bloom under both high and low
nitrate:phosphate ratios, and that the south-eastern Bering
Sea was an example of the latter situation. The bloom of2006 corroborates this, with a N:P ratio of about three(1.5:0.5). Siesser et al. (1992) and Kelly et al. (2003)
invoked upwelling of cool, nutrient-rich intermediatewaters to explain the presence of Braarudosphaera-richlayers in Lower Oligocene cores. Low-salinity waters andunusual current conditions have also been put forward as
a possible cause for past braarudosphaerid blooms (Wise& Kelts, 1972; Bukry, 1974; Siesser et al., 1992).
Although modern B. bigelowii never attains such numbers, unusual weather conditions, high sea-surface temperatures (SSTs), a shallow mixed-layer depth, and highlight-saturation levels have been cited as a possible causeof past Bering Sea E. huxleyi blooms (Merico et al.,2004). The bloom of 2006 occurred in a mixed layer ofabout 20m, but the SST was only 7˚C. However, it should
be noted that the salinity of the Bering Sea during ourstudy was about 31 PSU, a low value for oceanic waters,
but perhaps favourable to the growth of B. bigelowii,
which tends to prefer low-salinity waters.
Clearly, more information is needed to confirm theenvironmental preferences of B. bigelowii and to determine whether it is growing in situ with E. huxleyi blooms,
or is merely entrained in them as a declining relic of an
earlier phase, or as a member of a nearshore tychoplankton assemblage carried offshore.

83

Konno, Harada, Narita, Jordan

Figure 4: Most of the locations where living B. bigelowii has been reported from (including two from sediment trap studies*). Map created using
M. Weinelt’s ‘Online Map Creation’ site at www.aquarius.ifm-geomar.de. Pacific: Bering Sea (this study), Sea of Okhotsk (*Broerse et al., 2000),
off and around Japan (Nishida, 1979; Takano et al., 2006), south of Tasmania (Hiramatsu & De Deckker, 1996). Atlantic: Gulf of Maine and Bayof Fundy (Gran & Braarud, 1935), Gulf of St. Lawrence (Bérard-Therriault et al., 1999), Sargasso Sea (Gaarder, 1954; Hulburt, 1962), Roscoff(Lefort, 1972), Bay of Biscay (*Beaufort & Heussner, 2001), English Channel (Boalch, 1987), south of Ireland (Gaarder, 1954), off the Azores(Gaarder, 1954), off Portugal (Duarte-Silva et al., 2004), off Atlantic Morocco (Lecal-Schlauder, 1950). Mediterranean Sea: off North Africa(Borsetti & Cati, 1972; Knappertsbusch, 1993)

5. Conclusions
In this study, living specimens of Braarudosphaera
bigelowii were found in the Bering Sea, possibly the highest boreal-latitude occurrence reported so far. The coccospheres exhibited two distinct morphologies, possessing
pentaliths with flat or concave faces, and most of the pentalith dimensions correspond to the ‘intermediate B’ formof Takano et al. (2006). The coccospheres of B. bigelowii
occurred in low abundances and were mostly found in anarea associated with a mesoscale bloom of Emiliania huxleyi. The hydrographic conditions of this bloom-water
generally support the hypothesis that B. bigelowii prefers
low-salinity, nutrient-rich coastal waters.
Acknowledgements
The authors would like to thank the captain and crew of the R/V
Mirai and participating scientists for their help in acquiring thesamples used in this study. We are also grateful to Catherine
Gobin and Stéphane Armand for their help with the French literature. This manuscript has benefited from comments made by
Kyoko Hagino, Paul Bown and Jackie Lees.

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Plate 1
Braarudosphaera bigelowii flat form

Coccosphere with etched surface
Bering Sea, St.32 (65m)High magnification of specimen in Fig.3. Note ridge at element
margins
Bering Sea, KS-057

Coccosphere
Bering Sea, KS-057

Coccosphere with attached particles around element
marginBering Sea, KS-057

Coccosphere
Bering Sea, KS-057

Coccosphere with attached particles around element
margins
Bering Sea, KS-057

Living Braarudosphaera bigelowii...Bering Sea

Plate 2
Braarudosphaera bigelowii concave form

Coccosphere with attached particles aroundelement margins
Bering Sea, KS-057

Coccosphere with attached particles aroundelement margins
Bering Sea, KS-057

Coccosphere
Bering Sea, KS-057

Coccosphere
Bering Sea, KS-057

Coccosphere
Bering Sea, KS-057

High magnification of specimen in Fig.5. Noteridge at element margins
Bering Sea, KS-057

Coccosphere
Bering Sea, KS-057

High magnification of specimen in Fig.7. Noteprominent star-shaped gap in central area
Bering Sea, KS-057

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Appendix
List of taxa mentioned in the text, with their authorities.
Braarudosphaera Deflandre
Braarudosphaera bigelowii (Gran & Braarud) Deflandre
Braarudosphaera deflandrei Lecal
Coccolithus pelagicus (Wallich) Schiller
Emiliania huxleyi (Lohmann) Hay & Mohler
Micrantholithus Deflandre